1. Field of the Invention
This invention relates to medical instruments and, more specifically, to a continuous local anesthetization set to be used for setting a catheter in a place in the vicinity of a nerve for example, in a spinal subarachnoid space.
2. Description of the Prior Art
For example, the conventional catheters to be set in a spinal subarachnoid space include a catheter which is used by sticking a double needle, such as a epidural spinal anesthetic needle (Japanese Utility Model Application No. 41007/1988) having a Huber-pointed edge, or a spinal needle into the lumbodorsal skin from the rear side toward the spine (the tip of the needle reaches a spinal subarachnoid space through the skin, subcutaneous tissue, various kinds of ligaments and arachnoid membrane), pulling out an inner needle from the double needle, inserting this catheter into an outer needle which serves as a guide needle, and setting the catheter in the spinal subarachnoid space.
It is known that, when a catheter is stuck into a spinal subarachnoid space by using such a double needle, the patient has a post-spinal anesthesia headache which is ascribed to the leakage of a post-puncture medullary liquid from the puncture, and a rate of occurrence of this headache is proportional to the thickness of the needle. When the needle is thick, damage to the tissue in the punctured portion increases. Therefore, it is desirable that a very thin catheter be set in a spinal subarachnoid space by using a thin needle. However, when a catheter is made thin, it becomes soft and difficult to be inserted into a needle.
Under the circumstances, a catheter with a metallic stylet inserted therein has been used. Although this has enabled a catheter to be made rigid, the occurrence of bend of a catheter to be prevented, and the inserting of a catheter into a needle to be done easily, new problems have arisen.
For example, when a catheter is set in a spinal subarachnoid space, the front end thereof impinges upon a spinal wall or spinal cord, so that it becomes impossible to insert a catheter of a required length into a spinal subarachnoid space, and the degree of danger of compressing and hurting the spinal cord by the tip of a catheter increases. When the tip of a catheter impinges upon a spinal wall, the injection of an anesthetic cannot be sufficiently carried out. When a catheter is set in a one-sided state in a spinal subarachnoid space, an anesthetic is injected in only one direction, resulting in a partial anesthetization, even if the catheter setting operation itself is successfully carried out.
The above problems encountered in use of the conventional catheters are summarized as follows:
A. The opened free end portion of a catheter set in a spinal subarachnoid space impinges upon a spinal wall to prevent an anesthetic from being injected sufficiently into the spinal subarachnoid space.
B. A catheter of a required length cannot be inserted into a spinal subarachnoid space.
C. A catheter is set in a one-sided state, so that an anesthetic is injected into a spinal subarachnoid space partially, i.e., in one direction of the interior thereof, this causing the anesthetization effect to become partial.